1. Field of the Invention
This invention generally relates to surge protection devices and equipment for a home or office, and more specifically relates to surge protection systems which incorporate diagnostic circuitry.
2. Description of the Prior Art
Surge protectors commonly utilize metal oxide varistors (MOVs) as transient voltage surge suppression devices. Over time, MOVs degrade from continued exposure to power surges. Conventionally, when surge protectors fail due to a malfunction or failure of an internal or external MOV, the surge protector may cease to operate, notify the user of failure or a combination of both. When a surge protector fails or malfunctions, in some instances the entire device must be replaced. However, some conventional surge protectors have removable MOVs that may be replaced in the event of failure or malfunction as opposed to replacing the entire surge protector device which can be costly.
Some conventional surge protectors are capable of notifying the user when a MOV has degraded; however, these surge protectors offer no indication of the actual level of degradation. Users of such surge protection devices may assume that the level of degradation is minor and continue use of the protector without replacement. In such instances, the user places unnecessary risk on all the components connected to the surge protector as the MOV might actually be completely degraded and the next surge might damage the electronics. In other instances, a user might choose to replace the MOV assuming complete degradation. In this case, very often the MOV still has life remaining and the user spends unnecessary money to replace the MOV.
It is common for buildings to have many surge protectors, sometimes exceeding hundreds. These surge protectors provide a safeguard to a wide variety of sensitive electronics and data storage devices. Unfortunately, to effectively monitor the operational status of each surge protector, it is necessary to do spot inspections to verify that no warning indicators have been activated. Under most circumstances, this process is costly and extremely unlikely. Many users assume their electronics are infinitely safe from power surges simply because they utilize a surge protector, however many of these surge protectors are no longer effective and the user is simply not aware of their status.
U.S. Published Application No. 2007/0097584 discloses a surge protection device which includes a plurality of surge modules mounted onto a printed circuit board. Each module has a diagnostic circuit. Each module preferably includes four (4) parallel branches, each branch having a metal oxide varistor (MOV) and a thermal cut-off (TCO) device connected in series. The device also consists of various diagnostic devices such as a light emitting diode (LED) coupled to each of the surge protection modules. The opening of a TCO causes the LED to change color. The device also includes a peak detector circuit for processing information regarding a surge event, such as amplitude and time, which in turn may be stored in a memory unit. The published application also states that a microprocessor monitors the TCO's in the surge modules and causes warning messages to be displayed on an LCD screen when the surge protection has been degraded.
U.S. Published Application No. 2007/0086141 discloses a surge protection device which includes two MOVs and two MOV failure indicator circuits. Each circuit includes a fuse coupled to an LED. When the fuse opens, the LED indicates an MOV failure. The failure of the MOVs and subsequent lighting of the LEDs indicate the surge protector/strip requires replacement.
U.S. Published Application No. 2007/0002511 discloses a surge protection device which includes circuits utilizing gas discharge tubes (GDT) and MOVs. The invention also comprises a microcontroller or microprocessor for monitoring a plurality of voltages at certain points throughout the circuit. The microprocessor can determine whether or not the surge protectors are functioning or if there is a failure or malfunction. The user may be notified of failure via visual means such as a variable LED or audible tone. The power company or utility company also will be notified of the failure or malfunction by transmission means such as a low frequency signal sent over the power lines to a central unit. The surge protection module may be replaced and repaired.
U.S. Published Application No. 2003/0151874 discloses a surge protection device which utilizes MOVs and indicates their operational status via LEDs.
U.S. Published Application No. 2002/0141127 discloses a surge protection device which includes a housing which encloses a variety of different types of surge protector modules for communication systems, AC systems, and cables. Each surge protection module comprises a resistor, diode, light emitting diode and switch (including an MOV). The device includes LED warning lights to indicate surge module failure. The published application states that the surge protector modules may be easily removed and replaced from the main housing.
U.S. Pat. No. 6,881,076 discloses a device which is a coaxial module including removable surge protector modules. The entire surge protector modules are removable from the device via pins or screws connecting them to a printed circuit board.
U.S. Pat. No. 5,982,603 discloses a device which is a detachable surge protector module comprising two varistors and supportive circuitry. There is temperature sensitive tape that varies in color when surged with energy, thus providing a visual warning to the user when the surge protector has been degraded or destroyed. The entire device may be easily replaced without tools. The actual device includes a housing enclosing the varistors.
U.S. Pat. No. 5,053,919 discloses a surge protector module which may be removable from a main power assembly.
U.S. Pat. No. 5,010,438 discloses a device which is a detachable surge protector module for use in a circuit breaker box. The device includes MOVs coupled to fuses and LEDs to indicate the status of the suppressor module.
U.S. Pat. No. 4,907,118 discloses a device which is a plug in surge protector that is attached in line with the plug of a fixture and the electrical socket. It contains an MOV for providing surge protection along with an opening on its dorsal surface to view the MOV. When the MOV is surged, it changes color, indicating it is time to replace the device.
Most existing surge protectors or those having a replaceable MOV protection device are intended to tell the user when the device has failed, by using an audible alarm such as a small buzzer, or by a flashing LED, or by a special circuit arrangement to turn off the LED light when an MOV is burned out or damaged due to the surge energy which occurred on the AC power line.
The prior art, at best, either lets the user know of the current protective status of the MOV, or lets the user know that the MOV has failed. The obvious problem with the latter, just informing the user that the MOV has failed, is that while this condition exists, the equipment, supposedly protected by the MOV, is now unprotected and has the potential to be damaged by the next surge. The problem with the former is that the user just knows the current state of the MOV. When the user sees that the MOV has been degraded, the user will either replace the MOV immediately, or wait to replace it, hoping the next surge does not do any damage to the equipment connected to the surge protector.